我是 Unity 和 C# 新手，并嘗試查詢我的 Firebase 實(shí)時(shí)數(shù)據(jù)庫，但代碼不會(huì)阻止回調(diào)完成。我嘗試過實(shí)現(xiàn)回調(diào)，但這似乎不起作用。static public void ReadFromDb(int level, Action<int> callback) { int return_value = -1; string sessionId = PlayerPrefs.GetString("SessionID"); FirebaseDatabase.DefaultInstance.GetReference("users/"+sessionId).GetValueAsync().ContinueWith(task => { if (task.IsFaulted) { // Handle the error... Debug.Log("Task faulted"); callback(return_value); } else if (task.IsCompleted) { DataSnapshot snapshot = task.Result; string score_string = (snapshot.Child(level.ToString()).Value).ToString(); Debug.Log("score_string " + score_string); return_value = int.Parse(score_string); callback(return_value); } });}public void LevelComplete() { DatabaseCode.writeDatabase(SceneManager.GetActiveScene().buildIndex + 1, counter); DatabaseCode.ReadFromDb(SceneManager.GetActiveScene().buildIndex + 1, (result) => { prevlevelscore = result; Debug.Log("result " + result.ToString()); }); prevscore = prevlevelscore; Debug.Log("Returned value: " + prevlevelscore.ToString()); SceneManager.LoadScene(SceneManager.GetActiveScene().buildIndex + 1);}在LevelComplete(),Debug.Log("Returned value: " + prevlevelscore.ToString());之前執(zhí)行prevlevelscore = result;，我想確保prevlevelscore在執(zhí)行之前更新的值Debug.Log。
2 回答
慕桂英546537
TA貢獻(xiàn)1848條經(jīng)驗(yàn) 獲得超10個(gè)贊
將其余代碼也放入回調(diào)中：
public void LevelComplete()
{
DatabaseCode.writeDatabase(SceneManager.GetActiveScene().buildIndex + 1, counter);
DatabaseCode.ReadFromDb(SceneManager.GetActiveScene().buildIndex + 1, (result) => {
Debug.Log("result " + result.ToString());
prevscore = result;
SceneManager.LoadScene(SceneManager.GetActiveScene().buildIndex + 1);
});
}
富國滬深
TA貢獻(xiàn)1790條經(jīng)驗(yàn) 獲得超9個(gè)贊
您的問題是您的 ReadFromDb 方法在完成之前返回。您可以通過將所有代碼放入回調(diào)中來解決此問題（但您無法始終這樣做），或者可以使用異步等待模式。
使 ReadFromDb 異步：
static public async Task ReadFromDb(int level, Action<int> callback)
{
int return_value = -1;
string sessionId = PlayerPrefs.GetString("SessionID");
await FirebaseDatabase.DefaultInstance.GetReference("users/"+sessionId).GetValueAsync().ContinueWith(task => {
if (task.IsFaulted)
{
// Handle the error...
Debug.Log("Task faulted");
callback(return_value);
}
else if (task.IsCompleted)
{
DataSnapshot snapshot = task.Result;
string score_string = (snapshot.Child(level.ToString()).Value).ToString();
Debug.Log("score_string " + score_string);
return_value = int.Parse(score_string);
callback(return_value);
}
});
}
請(qǐng)注意前面的等待鍵，GetValueAsync().ContinueWith因?yàn)榇司_代碼是異步的，如果您想在獲取結(jié)果之前保留代碼執(zhí)行，則需要等待。
在你的來電者中：
public async Task LevelComplete()
{
DatabaseCode.writeDatabase(SceneManager.GetActiveScene().buildIndex + 1, counter);
await DatabaseCode.ReadFromDb(SceneManager.GetActiveScene().buildIndex + 1, (result) => {
prevlevelscore = result;
Debug.Log("result " + result.ToString());
});
prevscore = prevlevelscore;
Debug.Log("Returned value: " + prevlevelscore.ToString());
SceneManager.LoadScene(SceneManager.GetActiveScene().buildIndex + 1);
}
此方法也變?yōu)楫惒剑ㄒ驗(yàn)楫惒叫詴?huì)傳播）。同樣，await 關(guān)鍵字將繼續(xù)執(zhí)行，直到 readFromDb 方法完成。這意味著您的數(shù)據(jù)將準(zhǔn)備就緒。
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